CBQE-0:: fix ram quota test case

Change-Id: I5887ee1b287fcd08fda26e034783a0e6acab0099
Reviewed-on: http://review.couchbase.org/41230
Reviewed-by: Thuan Nguyen <soccon@gmail.com>
Reviewed-by: Parag Agarwal <agarwal.parag@gmail.com>
Tested-by: Parag Agarwal <agarwal.parag@gmail.com>